Comments

Add the win::WMIRefresher class and use it in SystemMonitor
This class will be used to retrieve the disk idle time on Windows (some
other performance counters will probably be added in the future).
The metric will initially be used in the tracing infra to make it
easier to analyze the I/O activity in the slow reports we're getting
from the wild.
The Windows specific code has been review by rogerta@ and forschaw@ in https://chromium-review.googlesource.com/c/chromium/src/+/1340373
Bug: 771478
Change-Id: Ie1988818f521097d6078ce67e597ec02115f4c07
Reviewed-on: https://chromium-review.googlesource.com/c/1349670
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634843}